1. Field of the Invention
The invention relates to an electric machine with a rotor and a stator in which electric coils and permanent magnets are located. The electric coils and the permanent magnets influence each other when the rotor revolves. The rotor contains the magnets and the stator contains the coils. The coils do not have an iron core and at least one section of the coils extends transversely across the circumference of the rotor.
2. Description of the Prior Art
A machine of this kind has been disclosed in EP-B-0 422 539. The purpose of the invention is to improve this machine.
In the solution to this problem proposed by the invention, the coils are fitted in the stator individually and then bent in such a way that they extend on both sides of the rotor and enclose the magnets located in the rotor to a large extent.
The fact that the magnets are enclosed by the individual coils leads to the achievement of a very high degree of efficiency, while both production and maintenance are simplified considerably by the provision of individual coils.
In accordance with an advantageous development of the invention, it is provided that the magnets are cylindrical and are located at least approximately tangentially on the circumference of the rotor. This configuration makes it simple to adjust the magnets and the coils.
In another advantageous development of the invention, the number of permanent magnets is equal to twice the number of coils. This configuration results in a sinusoidal shaped progression of the voltage and current curves.
In another advantageous development of the invention, the permanent magnets are attached to the rotor via support elements. This has the effect that the magnets can be easily replaced if this is required.
It is also very advantageous if in accordance with a further development of the invention the coils have a xcexa9-shaped cross-section and the magnets are immediately next to the inside of the coils. A particularly high degree of machine efficiency is reached as a result.
In another advantageous development of the invention, the support elements of the magnets are attached to the rotor in such a way that they can be replaced. This makes it particularly easy to remove the magnets from the machine and to fit them back on it again.
In another advantageous development of the invention, the coils are movable along the circumference of the stator so that the coils can be pushed together in order to clear a larger opening to the rotor for inserting the permanent magnets or for other service work.
It has also proved to be particularly advantageous if an interlocking facility is provided between the magnets and/or their support elements and the rotor, preferably in the radial direction. A secure connection is established between the magnet and/or support element and the rotor as a result. During operation of the machine, significant centrifugal forces arise as a result of its relatively large radius. The interlocking facility effectively compensates for these high centrifugal forces and prevent the permanent magnets form coming loose from the rotor.
It is also very advantageous if the magnets and/or their support elements are attached to the rotor in an axial direction. This guarantees that the magnets are simple to remove from the rotor.
It is also very advantageous if in accordance with a further development of the invention the connections for the coil are located so that they are accessible individually on the stator during assembly, operation and for service purposes. This makes it simple to check every individual coil if a fault occurs.
It has proved to be very advantageous if in accordance with a further development of the invention the magnets located behind each other have different polarity in each case. The machine achieves high power yield as a result.
It is also particularly favorable if in accordance with a further development of the invention a pole reversal device is provided in the supply line to the coils. As a result of this, the electric machine can on the one hand be operated with direct current voltage before the pole reversal device and with alternating current voltage after the pole reversal device when it is used as a motor, while alternating current voltage can on the other hand be tapped before the pole reversal device and direct current voltage can be tapped after the pole reversal device when the electric machine is used as a generator.
It has proved to be very favorable if in accordance with a further development of the invention the coil is annular and the profiles of the rotor and coil are adapted to each other.
A further advantageous development of the invention is characterized by the fact that several rotors and coil configurations are located behind each other in the axial direction of the machine.
It is also very favorable if in accordance with a further development of the invention at least two machines preferably in the form of motors with different diameters are located behind each other on a mutual machine shaft. The different diameters mean that the motors have different torque, which can be very advantageous in particular when the machine starts up.
It has also proved to be extremely advantageous if the coils are formed from several coils that are only one wire thick in each case. Easier and more precise shaping of the coils is possible as a result. It is very advantageous in this context if the connections for the individual coils are wired individually and are in particular designed so that they can be connected in series ands/or in parallel. It has also proved to be very advantageous if the individual coil layers are in particular glued together with an adhesive that conducts heat effectively. This construction guarantees optimum coil design and good heat dissipation.
In a further advantageous development of the invention, a coil layer is applied for example to a blank and the connectors for the coil are passed to the outside of the coil. The coil layer can be fixed in place by means of glue. A commercially available glue that conducts heat well can be used as the adhesive to fix the coil layer or layers in place Additional layers may be applied to the first layer in the same manner and the connectors for the additional layers are passed to the outside. The connectors of the coil layers are passed to a terminal which is provided in the vicinity of the coil. This terminal allows the coil layers to be individually switched in series or in parallel with one another.
In a further advantageous development of the invention, incoming lines to the individual coils and/or coil layers are passed to the outside in such a manner that a terminal into which the incoming lines lead can be provided at the stator or in the vicinity of the stator. Switches may be provided at or in the vicinity of the stator which allow the coils to be switched in series or in parallel. The switching between serial and parallel configurations of the coils can also take place automatically during operation of the machine, for example as a function of coil voltage or rotor rotation speed.
In a further advantageous development of the invention, a close coil gap is provided which results in a smooth voltage sine curve without any significant harmonics when the machine is used as a generator. Conventional generators produce voltage curves with harmonics.
In a further advantageous development of the invention, all of the coils are active a the same time resulting in high output density when the machine is used as a generator or high torque if the machine is used as a motor.
In a further advantageous development of the invention, shielding is provided on the outside of the stator that in particular provides magnetic shielding. It is very advantageous in this context if the shielding is made from wire, particularly a plurality of soft iron wires. It is also very advantageous in this context if the shielding wires are located in concentric circles around the shaft of the machine. It is also proved to be advantageous if the shielding is made from sheet metal, particularly soft iron sheet metal. Shielding the stator against magnetic and electric fields that act outwards reduces the effect on the machines in the surrounding area considerably.
In accordance with another development of the invention, it is very advantageous if a cable support is provided on the circumference of the rotor-stator assembly. Tidy and simple cable guidance between the coils in and out of the machine is guaranteed in this way.
In another very advantageous development of the invention, a housing is provided that enclose the entire rotor-stator assembly. This on the one hand provides protection against contact, while it on the other hand effectively keeps dirt, etc. away from the electric machine. It is advantageous in this context if the housing has at least one air inlet opening in the immediate vicinity of the machine shaft. It is also very advantageous in this context if the housing has at least one air outlet opening at least close to the point where the circumference is largest. The air sucked in though the air inlet opening is accelerated towards where the rotor circumference is largest by the rotary movement of the rotor and leaves the housing via the air outlet opening. The machine is cooled effectively as a result. Optimum air flow over and around the coils is guaranteed as a result.
In a further advantageous development of the invention, the air outlet is connected to the air inlet via a heat exchanger provided between them. This is an effective way to remove the waste heat of the machine and possibly to use it for another purpose. It has proved to be very advantageous in this context if the heat exchanger transfers the heat of the machine to a gaseous or liquid medium. It is also very advantageous if the heat exchanger transfers the machine heat to a solid medium and in particular if the heat exchanger is designed to be a geothermal heat exchanger.
It is extremely advantageous if in accordance with a further development of the invention a particle filter is provided on the air inlet. Particles that are harmful to the machine are kept away form the inside of the housing as a result. It has proven advantageous in this context if the particle filter has at least one fine metallic screen. This guarantees that the fine screen can be cleaned and reused even when it has become very dirty.
It is also very advantageous if a magnet, particularly a permanent magnet, is located with one pole on the fine screen. This is an effective way to keep out magnetic particles that could have the greatest impact on the machine.
It is also very advantageous in this context if a connection is established between a second fine screen and the second pole of the magnet. Any magnetic particles that manage to get through the first fine screen nevertheless are as a result stopped by the second fine screen.
It is also extremely advantageous if the fine screens are configured in such a way that they can be separated from the magnet. The particles that have been caught are particularly easy to remove form the fine screen(s) after they have been separated from the magnet.
In another advantageous development of the invention, a filter is provided that is able to filter particles that can be influenced electrically and/or magnetically out of the flow of air. Electrically charged particles that have a negative effect on the machine can also be kept out of the inside of the housing as a result.
In another advantageous development of the invention, the housing is designed in such a way that effective heat transmission is guaranteed between the housing and the surroundings. This enables the machine to be operated without any danger of overheating even when it is completely enclosed.